The existing common inductive sensors are divided into inductive sensors with ferrite pot cores and inductive sensors without ferrite pot cores.
The inductive sensor with a ferrite pot core is used for detecting metal by using a coil system consisting of a ferrite pot core and a coil wound on the ferrite pot core. The ferrite pot core has a self-shielded structure and has only an opening in one direction so that the magnetic field generated by the coil system is present only in the opening direction. As shown in FIG. 1a and FIG. 1b, the sensor comprises a housing 1.1, a connecting cable 1.3 and a coil system 1.8, which is formed by winding a coil 1.7 inside a ferrite pot core 1.5. This sensor has a magnetic field only in a front detection area 1.2 of the housing 1.1 of the sensor. This sensor is not affected by slight electromagnetic interference, but if there is a strong electromagnetic interference near the sensor, such as a welding robot, this may affect the magnetic properties of the ferrite core leading to interfere with the sensor.
As to an inductive sensor without a ferrite pot core, a coil is wound around a plastic pipe. Such sensor is relatively wide in magnetic field distributions. In order to obtain a directional magnetic field, metal rings or metal pipes having different thicknesses and favorable conductivity are additionally arranged around the coil of the sensor. For example, copper is used to completely surround the side surface of the coil to weaken the radial magnetic field of the detection coil, leaving only the magnetic field in front of the detection coil. As shown in FIG. 1a and FIG. 1c, the sensor comprises a housing 1.1, a connecting cable 1.3 and a coil system 1.8 which is formed by winding a coil 1.7 around the plastic pipe 1.10. The coil 1.7 is also surrounded by a copper ring 1.9, such that this sensor has a magnetic field only in a front detection area 1.2 of the housing 1.1 of the sensor. However, this sensor also reduces the influence of the surrounding metal on the sensor, and also weakens the magnetic field on a detection area 1.2 and reduces the sensitivity of the sensor.